The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advances in IC design and material have produced generations of ICs where each generation has smaller and more complex circuits than previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased.
This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs. Such scaling down has also increased the complexity of IC processing and manufacturing. For these advances to be realized, similar developments in IC processing and manufacturing are needed. Present methods of manufacturing use silicon carbide as an etch stop layer and as a copper barrier layer, but silicon carbide has low etch selectivity and can be easily etched away. Moreover, copper often diffuses into the tungsten used in metal plugs, which has undesired effects on yield and reliability. Thus, it is desired to have improvements in this area.